This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. XAS is uniquely suited for investigating in situ metal speciation in plant and environmental samples, eliminating extraction and sample preparation procedures that may change the speciation. We propose to use XAS to investigate the accumulation and transformation of zinc, cadmium and mercury in whole plants and plant cells, to determine tolerance mechanism as a function of tissue type, and as a function of periodic trends. We will also use XAS to study uptake and transformation of mercury in live and decaying fish, and in human hair. This work will contribute to a fundamental understanding of the speciation of heavy metals in plants, fish, and human hair. It will provide insight into the biomagnification and cycling of mercury in the aquatic environment. An understanding of the biotic and abiotic transformation processes will provide a more complete picture of the fate, transformation and potential remediation of mercury in the SF Bay environment. Furthermore, these studies will provide a link between the molecular response of plants to metals and the fate of those metals in plants, providing insight into the role of a specific response of plants in tolerance and accumulation of metals.